The extra
rows starting in row 21 first list the indices for the components,
then repeat their names. Row 23 holds the amount pulled from
each component. This is a new feature for the line structure
and it can be used to pull intermediate flow from any component.
The example pulls 100 units from component 7 and all other flows
are based on this amount.
Row 24 holds the O/I ratios for the components.
Note that components 4 and 5 each have the value of 0.9. This
means for every unit that enters each operation, 0.9 will leave.
The flow rates are adjusted accordingly in row 25. Because the
flow leaving operation 5 is 100, the flow entering must be 100/0.9
or 111.11. Similarly, the flow entering operation 4 must be
111.11/0.9 or 123.46. The flows are computed with Excel formulas
in the *Flow Rate *cells in row 25.
There are several features that should be recognized.
We have not changed the lot sizes to reflect the flow changes.
For example, the flow enters operation 5 in lots of 6 and leaves
in lots of 3. Since more flow enters due to the ratio, the lots
must arrive more frequently than if the ratio were 1. The total
flow shown in cell I23 is not the same as the flow in each component.
Since the system cycle time is computed with this value, the
system cycle time is not the time for a finished unit to pass
through the system, but it is an adjusted time that also reflects
units that start but do not finish.
In the following we illustrate the several drive/structure
options when ratios are allowed to be other than 1. These are
the same examples used to illustrate the options without ratios,
however, some of the ratios have been changed to illustrate
the effect. |